At present, the dispensing of comestible beverages, particularly table wines, fruit juice or pasteurized milk, from small rigid, semi-rigid or flexible containers, such as wine containers of synthetic material, generally takes place by means of taps fixed on the outlet of these receptacles.
To this end, there are known taps constituted by a body for mounting in the outlet of a receptacle and by a piston for releasing liquid, loaded by a spring and guided in the body, the piston acting on a resilient sealing membrane secured to the body. The mounting body in the outlet is provided with a securement handle coacting by snapping on the outlet.
Such taps permit correct dispensing of the liquid and are perfectly suitable, either for a bottling operation or for a series of withdrawals, whether these latter be carried out in a sterile environment, such as a sterile chamber for aseptic filling, or not, for example for filling glasses or small receptacles, which is to say for private or restaurant use for small flows of a single beverage or a single vintage.
There are also known taps for distributing liquids, particularly comestible liquids that are sterile or not, with an automatic closure, which are constituted by a body for mounting in the outlet of a receptacle and by a piston for releasing liquid acting on a resilient sealing membrane secured to the body, these taps being provided with means for holding the piston in open position.
There exist still other taps of the beverage type, in which the passage of the liquid is effected by aligning the passage openings by means of a lever or a manipulating handle.
All these known taps permit fulfilling correctly their essential function of sealingly closing a receptacle with the possibility of withdrawing the liquid contents. However, given the relatively large number of their constituent pieces, requiring corresponding mounting operations, their cost is greatly affected by these operations, such that in these taps, the cost of the material forming their constituent pieces is only a small part of their sales price.
It is also known to provide a tap for the dispensing of liquids, comprising a flap or sealed closure member for a dispensing opening of the liquid, manipulated by means of a control device forming a part of a front closure membrane. Such a tap has, however, the drawback of not permitting guaranteeing perfect and lasting closure of the outlet for the liquid after manipulation. Thus, in these taps, the flap or closure membrane is not guided and moreover, the manipulating means is subject to rapid fatigue, preventing the continued elastic memory necessary to guarantee sealed closure.
There is also known, from EP-A-0 213 783, a tap for carbonated liquids comprising a diaphragm manipulated by means of two handles. This tap is provided with an interface serving as a diaphragm and acting on a piston which is secured to said diaphragm, this diaphragm being actuated by means of two handles extending above it. To this end, it is necessary to apply a strong opening force by means of the handles, so as to deform the diaphragm in the opening direction of the valve of the tap.
This difficulty of opening the diaphragm is due to the fact that it is made of the same material as the body of the tap, in a single molding operation. It results that the diaphragm or dome, secured to the piston, is not naturally resilient but only by its construction during production, the elasticity or semi-rigidity necessary for its deformation for actuating the piston being obtained only by the provision of circular lines of weakening in the form of grooves.
Thus, such a tap cannot be monostable, which is to say have a resilience permitting reliable spring force, without counter-pressure. Thus, the flexibility of the diaphragm or dome alone is not sufficient to ensure correct alternate opening and closing of the tap and only the pressure of the product enclosed in the container provided with this tap is adapted to guarantee the closure by acting on the piston and to guarantee sealing.